/*global qs, qsa, $on, $parent, $delegate */

(function (window) {
  'use strict';

  /**
       * View that abstracts away the browser's DOM completely.
       * It has two simple entry points:
       *
       *   - bind(eventName, handler)
       *     Takes a todo application event and registers the handler
       *   - render(command, parameterObject)
       *     Renders the given command with the options
       */
  function View(template) {
    this.template = template;

    this.ENTER_KEY = 13;
    this.ESCAPE_KEY = 27;

    this.$todoList = qs('.todo-list');
    this.$todoItemCounter = qs('.todo-count');
    this.$clearCompleted = qs('.clear-completed');
    this.$main = qs('.main');
    this.$footer = qs('.footer');
    this.$toggleAll = qs('.toggle-all');
    this.$newTodo = qs('.new-todo');
  }

  View.prototype._removeItem = function (id) {
    var elem = qs('[data-id="' + id + '"]');

    if (elem) {
      this.$todoList.removeChild(elem);
    }
  };

  View.prototype._clearCompletedButton = function (completedCount, visible) {
    this.$clearCompleted.innerHTML = this.template.clearCompletedButton(completedCount);
    this.$clearCompleted.style.display = visible ? 'block' : 'none';
  };

  View.prototype._setFilter = function (currentPage) {
    qs('.filters .selected').className = '';
    qs('.filters [href="#/' + currentPage + '"]').className = 'selected';
  };

  View.prototype._elementComplete = function (id, completed) {
    var listItem = qs('[data-id="' + id + '"]');

    if (!listItem) {
      return;
    }

    listItem.className = completed ? 'completed' : '';

    // In case it was toggled from an event and not by clicking the checkbox
    qs('input', listItem).checked = completed;
  };

  View.prototype._editItem = function (id, title) {
    var listItem = qs('[data-id="' + id + '"]');

    if (!listItem) {
      return;
    }

    listItem.className = listItem.className + ' editing';

    var input = document.createElement('input');
    input.className = 'edit';

    listItem.appendChild(input);
    input.focus();
    input.value = title;
  };

  View.prototype._editItemDone = function (id, title) {
    var listItem = qs('[data-id="' + id + '"]');

    if (!listItem) {
      return;
    }

    var input = qs('input.edit', listItem);
    listItem.removeChild(input);

    listItem.className = listItem.className.replace('editing', '');

    qsa('label', listItem).forEach(function (label) {
      label.textContent = title;
    });
  };

  View.prototype.render = function (viewCmd, parameter) {
    var self = this;
    var viewCommands = {
      showEntries: function () {
        self.$todoList.innerHTML = self.template.show(parameter);
      },
      removeItem: function () {
        self._removeItem(parameter);
      },
      updateElementCount: function () {
        self.$todoItemCounter.innerHTML = self.template.itemCounter(parameter);
      },
      clearCompletedButton: function () {
        self._clearCompletedButton(parameter.completed, parameter.visible);
      },
      contentBlockVisibility: function () {
        self.$main.style.display = self.$footer.style.display = parameter.visible ? 'block' : 'none';
      },
      toggleAll: function () {
        self.$toggleAll.checked = parameter.checked;
      },
      setFilter: function () {
        self._setFilter(parameter);
      },
      clearNewTodo: function () {
        self.$newTodo.value = '';
      },
      elementComplete: function () {
        self._elementComplete(parameter.id, parameter.completed);
      },
      editItem: function () {
        self._editItem(parameter.id, parameter.title);
      },
      editItemDone: function () {
        self._editItemDone(parameter.id, parameter.title);
      }
    };

    viewCommands[viewCmd]();
  };

  View.prototype._itemId = function (element) {
    var li = $parent(element, 'li');
    return parseInt(li.dataset.id, 10);
  };

  View.prototype._bindItemEditDone = function (handler) {
    var self = this;
    $delegate(self.$todoList, 'li .edit', 'blur', function () {
      if (!this.dataset.iscanceled) {
        handler({
          id: self._itemId(this),
          title: this.value
        });
      }
    });

    $delegate(self.$todoList, 'li .edit', 'keypress', function (event) {
      if (event.keyCode === self.ENTER_KEY) {
        // Remove the cursor from the input when you hit enter just like if it
        // were a real form
        this.blur();
      }
    });
  };

  View.prototype._bindItemEditCancel = function (handler) {
    var self = this;
    $delegate(self.$todoList, 'li .edit', 'keyup', function (event) {
      if (event.keyCode === self.ESCAPE_KEY) {
        this.dataset.iscanceled = true;
        this.blur();

        handler({id: self._itemId(this)});
      }
    });
  };

  View.prototype.bind = function (event, handler) {
    var self = this;
    if (event === 'newTodo') {
      $on(self.$newTodo, 'change', function () {
        handler(self.$newTodo.value);
      });

    } else if (event === 'removeCompleted') {
      $on(self.$clearCompleted, 'click', function () {
        handler();
      });

    } else if (event === 'toggleAll') {
      $on(self.$toggleAll, 'click', function () {
        handler({completed: this.checked});
      });

    } else if (event === 'itemEdit') {
      $delegate(self.$todoList, 'li label', 'dblclick', function () {
        handler({id: self._itemId(this)});
      });

    } else if (event === 'itemRemove') {
      $delegate(self.$todoList, '.destroy', 'click', function () {
        handler({id: self._itemId(this)});
      });

    } else if (event === 'itemToggle') {
      $delegate(self.$todoList, '.toggle', 'click', function () {
        handler({
          id: self._itemId(this),
          completed: this.checked
        });
      });

    } else if (event === 'itemEditDone') {
      self._bindItemEditDone(handler);

    } else if (event === 'itemEditCancel') {
      self._bindItemEditCancel(handler);
    }
  };

  // Export to window
  window.app = window.app || {};
  window.app.View = View;
}(window));
